# Explain how the structural features of the mitochondrion are related to its role in aerobic cell respiration.

> IB DP Biology Higher Level (2023 syllabus) — B2.2 Organelles and compartmentalisation · Explain · 4 marks

## Mark scheme (4 marks)

1. The inner mitochondrial membrane is folded into cristae, which greatly increases the surface area available for the electron transport chain and ATP synthase.
2. The matrix is the site of the Krebs cycle and contains the enzymes, coenzymes, and DNA/ribosomes needed for these reactions.
3. The intermembrane space accumulates protons (H⁺) pumped by the electron transport chain, establishing a proton gradient that drives ATP synthesis via ATP synthase.
4. The double membrane compartmentalises the mitochondrion, maintaining the distinct chemical environments needed for each stage of aerobic respiration.

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